Because that is counter productive to increasing productivity.
Having team members focused on getting themselves ranked higher than their teammates, means incentivizing them to not help each other or do something they might not get credit for, even if it's in the best interest of the product or the team.
Even if you've tied team compensation to the results of the company, you still have to decide how it will be shared among the team members. So how do you go about compensation, bonuses, etc.? The same for everybody?
